z/OS Version 2 Release 3 MVS Programming: Extended Addressability Guide IBM SA23-1394-30 Note Before using this information and the product it supports, read the information in “Notices” on page 233. This edition applies to Version 2 Release 3 of z/OS (5650-ZOS) and to all subsequent releases and modifications until otherwise indicated in new editions. Last updated: 2019-02-16 © Copyright International Business Machines Corporation 1988, 2017. US Government Users Restricted Rights – Use, duplication or disclosure restricted by GSA ADP Schedule Contract with IBM Corp. Contents List of Figures....................................................................................................... ix List of Tables........................................................................................................ xi About this document...........................................................................................xiii Who should use this document.................................................................................................................xiii How this document is organized............................................................................................................... xiii How to use this document.........................................................................................................................xiv z/OS information........................................................................................................................................xiv How to send your comments to IBM......................................................................xv If you have a technical problem.................................................................................................................xv Summary of changes...........................................................................................xvi Summary of changes for z/OS Version 2 Release 3..................................................................................xvi Summary of changes for z/OS Version 2 Release 2..................................................................................xvi z/OS Version 2 Release 1 summary of changes.......................................................................................xvii Chapter 1. An introduction to extended addressability............................................1 Basic concepts............................................................................................................................................. 3 Asynchronous cross memory communication...................................................................................... 3 Synchronous cross memory communication........................................................................................ 3 Access register ASC mode......................................................................................................................3 Data-in-Virtual........................................................................................................................................ 4 Virtual lookaside facility......................................................................................................................... 4 Data spaces and hiperspaces.................................................................................................................4 Basic decision: data space or hiperspace................................................................................................... 5 What can a program do with a data space or a hiperspace?.................................................................5 What are the differences?...................................................................................................................... 6 Which one should your program use?....................................................................................................8 Choosing VIO instead of a data space or a hiperspace......................................................................... 9 Chapter 2. Linkage stack......................................................................................11 Linkage stack considerations for asynchronous exit routines..................................................................12 Instructions that add and remove a linkage stack entry.......................................................................... 12 Branch and stack (BAKR) instruction...................................................................................................12 Program return (PR) instruction...........................................................................................................12 Example of using the linkage stack......................................................................................................13 Contents of the linkage stack entry...........................................................................................................14 Instructions that manipulate the contents of a linkage stack entry........................................................ 14 Extract stacked registers (EREG) instruction...................................................................................... 14 Extract stacked state (ESTA) instruction............................................................................................. 15 Modify stacked state (MSTA) instruction............................................................................................. 16 Expanding a linkage stack to a specified size........................................................................................... 16 Relationship between the linkage stack and ESTAE-type recovery routines...........................................17 Dumping the contents of the linkage stack...............................................................................................17 Chapter 3. Synchronous cross memory communication.........................................19 When should you use synchronous cross memory communication?...................................................... 19 Terminology, macros, and assembler instructions................................................................................... 19 Cross memory terminology..................................................................................................................19 Macros used for synchronous cross memory communication........................................................... 21 Instructions used for cross memory communication......................................................................... 22 iii An overview of cross memory communication......................................................................................... 22 PC routines........................................................................................................................................... 22 Summary of cross memory communication........................................................................................25 The cross memory environment................................................................................................................26 Entry tables...........................................................................................................................................26 Linkage tables.......................................................................................................................................26 The PC number..................................................................................................................................... 26 Program authorization — the PSW-key mask (PKM)........................................................................... 27 Address space authorization................................................................................................................27 Considerations before using cross memory..............................................................................................31 Environmental considerations............................................................................................................. 31 Restrictions...........................................................................................................................................31 Requirements....................................................................................................................................... 31 Establishing cross memory communication............................................................................................. 31 Making a PC routine available to all address spaces...........................................................................32 Making a PC routine available to selected address spaces................................................................ 33 Examples of how to establish a cross memory environment...................................................................35 Example 1 - Making services available to selected address spaces.................................................. 36 Example 2 - Making services available to all address spaces............................................................ 43 Example 3 - Providing non-space switch services.............................................................................. 45 PC linkages and PC routine characteristics...............................................................................................45 PC linkage capabilities........................................................................................................................